For years we’ve been told that fish oil supplements are good for everything from limp hair and joint pain to preventing heart disease.

But now some Ottawa-based researchers are suggesting we’ve swallowed a fish story, hook, line and advertisement.

Thousands of research articles extol the health benefits of fish oil. But according to George Fodor and his colleagues at the University of Ottawa Heart Institute, there’s no satisfactory scientific evidence to support all those claims.

“The idea that fish oil has some protective effect on heart disease was very doubtful from the beginning,” Fodor said Monday. “The hypothesis (of fish oil’s healthful benefits) was created on very shaky grounds.”

Fish oil, which is derived from the tissues of oily fish, contains omega-3 fatty acids that are thought by many health specialists to benefit a number of bodily functions, particularly the heart. Behind this idea is a widely known study from the 1970s by two Danish nutritionists who looked at the seemingly low prevalence of heart disease among Greenland Inuit and concluded that their “Eskimo diet,” consisting of large amounts of seal and whale blubber, might well be the reason.

Fodor examines the diet in an article in the August issue of the Canadian Journal of Cardiology. He and his team reviewed four decades of studies — some 5,000 articles in all — on the cardiovascular health of Canadian and American Inuit and Greenland Eskimos. While a few found low rates of heart disease in this population, most of them concluded that the prevalence of coronary artery disease among Inuit is either much the same as that of non-Inuits or, in some case, even greater. In reality, the preponderance of evidence indicates that Inuit suffer more from heart disease that non-Inuit, says Fodor, the lead author.

“The result of these investigations confirm that the prevalence of coronary artery disease in the Inuit population is as great or greater compared with non-Eskimo populations,” he writes in an article entitled “‘Fishing’ for the Origins of the ‘Eskimos and Heart Disease’ Story: Facts or Wishful Thinking?”

Such a finding, says Fodor, raises question about the belief in the health benefits of fish oil. “Although the notion that Eskimos are protected against coronary artery disease cannot be supported by scientific evidence, a large number of recent publications reporting on the effects of fish oil consumption still perpetuate this belief,” Fodor writes, noting that many still cited the Danish investigators’ work as proof.

Indeed, according to Fodor, the “Eskimo diet” is a formula for ill health. “The alleged absence of cardiovascular disease in Greenland Eskimos is a paradoxical finding, because this is a population mainly sustained on a diet high in animal fat, absence of fruits and vegetables, and other important nutrients; in other words, a diet that violates all principles of balanced and heart-healthy nutrition.”

Fodor’s skepticism is supported by other researchers. For example, a 2012 study in The Journal of the American Medical Association determined that taking fish oil supplements doesn’t reduce the risk of heart attacks or strokes.

On the other hand, a recent study published in the journal Alzheimer’s & Dementia concluded that fish oil supplements, when taken daily, were “associated with better performance on standard tests of memory and thinking abilities over time, compared to those who didn’t take supplements.”

Various organizations also extol the virtues of fish oil. The American Heart Association urges those with coronary artery disease to take daily fish oil supplements.

Health Canada’s Food Guide recommends at least two fish servings a week. Similarly, the European Society of Cardiology and the European Society of Hypertension advise patients with hypertension to eat fish at least twice a week.

In his article, Fodor is careful not to say categorically that fish oils have no health benefits, cardiovascular or otherwise; only that the claims regarding those benefits are “based on a hypothesis that was questionable from the beginning.”

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